Seismic evaluation of concrete gravity dam under the effect of far and near field earthquakes considering dam saturation

Since concrete saturation can significantly alter its properties and change its behavior under various loadings, this study examines the effects of dam body saturation on its seismic behavior. To this end, the characteristics of saturated concrete, including elasticity modulus, compressive and tensile stresses, and compressive and tensile strains, were initially determined. Then, the Koyna concrete gravity dam was selected as a case study, and the boundary between the saturated and unsaturated environments was determined considering three different levels of reservoir height. Modeling, determination of the saturation boundary in the dam body, and seismic analyses were conducted using Abaqus software. The Eulerian–Lagrangian method was employed for modeling both the structural and fluid domains. For a better analysis and conclusion regarding the effects of dam body saturation on structural responses, earthquakes with different frequency contents scaled to a maximum acceleration of 0.5 g were used for both far-field and near-field scenarios. The results indicated that dam body saturation altered the fundamental frequencies of the structure and significantly influenced its responses. Saturation notably reduced maximum displacements in linear conditions in most cases. In nonlinear analysis, maximum displacements were generally lower in saturated conditions compared to unsaturated conditions. In many instances, dam body saturation reduced structural damage, which was more pronounced for dams with shallower reservoir depths.